It's a discovery that may hold promise for countless prospective parents unable to conceive naturally.

Canadian researchers have found that adding thyroid hormone to bovine eggs during the early stages of in-vitro fertilization can greatly increase the survival rate and health of embryos.

Although the discovery was made using cows, researchers have high hopes that they will be able to apply the results to humans because they have many reproductive similarities to the animals. The research will appear in the online February issue of the journal Experimental Biology and Medicine, and has also appeared in November's online issue of the journal Human Reproduction.

"It could represent a significant step forward in the efficiency of the process," says Allan King, professor in the department of biomedical sciences at the Ontario Veterinary College at the University of Guelph and Canada Research Chair in animal reproductive biotechnology. "We hope that it will make it a more efficient treatment for human infertility."

In-vitro fertilization, or IVF, and other forms of assisted human reproduction have become increasingly common in the past few years among those facing infertility or other serious difficulties in becoming pregnant naturally. The process involves removing eggs from a woman and fertilizing them outside of the body. The fertilized egg is transferred into the uterus in hopes of beginning a successful pregnancy. The treatment can be extremely costly and is not guaranteed to work.

That's why the discovery that thyroid hormone may give a boost to the process is so exciting.

"If we can increase the efficiency of [IVF]by only 10 per cent, that will increase … the success rate," Prof. King says.

The team of researchers found that adding thyroid hormone after eggs were fertilized increased the number of "good" embryos by 30 per cent. Adding thyroid hormone also seemed to improve the quality of the embryos, meaning that they were more likely to have a higher number of cells, fewer damaged cells and increased survival after being frozen and thawed before being implanted in the uterus.

It's still unclear why thyroid hormone seems to provide this added edge. But Prof. King and his colleagues believe the hormone also acts as a booster during natural conception.

They believe thyroid hormone activates or "turns on" certain genes that are essential to the development of a healthy fetus, which means that adding the hormone during IVF procedures could help mimic the conditions of natural conception, says Fazl Ashkar, a medical doctor and PhD student who helped conduct the research.

The researchers added that some studies had shown women with certain fertility problems have low levels of thyroid hormone, which adds credence to the theory that it plays a critical role in establishing a successful pregnancy.

Now, Prof. King says, he intends to embark on a new research mission to determine if the findings can be replicated in humans.

If his hypothesis proves correct, it could pave the way for changes that may decrease the number of costly IVF rounds some individuals must go through in order to become pregnant.

The cost and efficiency of IVF has been the subject of heated debate in recent months. An Ontario report released last fall by a panel assembled by Premier Dalton McGuinty urged the province to cover the cost of up to three cycles of IVF. Quebec already has such a program in place.